The use of fossil fuel as the combustible fuel in engines results in the combustion products of carbon monoxide, carbon dioxide, water vapor, smoke and particulate, unburned hydrocarbons, nitrogen oxides and sulfur oxides. Of these above products carbon dioxide and water vapor are considered normal and unobjectionable. In most applications, governmental imposed regulations are restricting the amount of pollutants being emitted in the exhaust gases.
In the past, the majority of the products of combustion have been controlled through design modifications and fuel selection. For example, at the present time smoke has normally been controlled by design modifications in the combustion chamber, particulates are normally controlled by traps and filters, and sulfur oxides are normally controlled by the selection of fuels being low in total sulfur. This leaves carbon monoxide, unburned hydrocarbons and nitrogen oxides as the emissions of primary concern in the exhaust gas being emitted from the engine.
Many systems have been developed for recycling a portion of the exhaust gas through the engine thereby reducing the emission of these components into the atmosphere. The recirculation of a portion of exhaust gas is used to reduce pollution emitted to the atmosphere. In many of such past system a volume of the exhaust gas from the engine was redirected to the intake air of the engine through the turbocharger and to the engine. It is anticipated that future exhaust emission standards will require the use of cooled exhaust gas recirculation to meet the emission standards. One method of cooling the exhaust gas is to use an engine jacket water cooler. The problem with this approach is that the temperature of the engine jacket water is increased and the heat must be rejected to the atmosphere via a heat exchanger or radiator. The tendency of vehicle manufactures is to reduce the frontal area of their vehicles to improve visibility and aerodynamics. Thus, with this tendency the available heat rejection area of the heat exchanger is being reduced and any increase in heat exchanger size requiring a larger frontal area is not well accepted. And, if the additional heat added to the engine cooling system by the exhaust gas cooling is not rejected, the extra heat will cause engine overheating under some operating parameters.
The present invention is directed to overcoming one or more of the problems as set forth above.